Since 2009, per-enrollee Medicare spending has grown less quickly than the economy, at only 1.4 percent per year. However, Medicare Part D spending on prescription drugs is expected to 5.8 percent per year over the next decade.

That the drug benefit is growing faster than other medical services is indicative of the dramatic price increases for drugs that treat cancer and other common illnesses such as hepatitis and arthritis.

Medicare's planned reforms to rein in costs are only just beginning, however. It was this year that the program is putting in place a program that reimburses hospitals for certain surgeries based on hospital readmission rates post-operation. And beginning last year, Medicare reserves 1.5 percent of its funds to reward top-performing hospitals based on quality of care and efficiency.

In 2019, Medicare plans to begin a more aggressive outcome-based system of reimbursement, called MACRA, that will hopefully bend down the cost curve and keep the massive health care program that serves tens of millions of seniors solvent for many more years to come.

The other most notable proposal to rein in Medicare's costs is to raise the age of eligibility. In the health care overhaul proposed by House Republicans earlier this week, the age would increase from 65 to 67.